A three-dimensional structured memory device is proposed in which a memory hole is formed in a stacked body in which an electrode layer functioning as a control gate in a memory cell is stacked in plural via an insulating layer and a silicon body serving as a channel is provided on the side wall of the memory hole via a charge storage film.
A technology is proposed in which, in a circular cylindrical memory cell of such a three-dimensional structured memory device, the whole or part of a tunnel insulating film is replaced with an air gap in order to suppress leakage current during cell operation. However, since a current passes through the air gap repeatedly during memory cell operation, local dielectric breakdown may occur in this process. Consequently, it may be difficult to ensure the reliability of the memory cell.